12.01: Measuring Aortic Distensibility with CMR Using Central Pressures Estimated in the Magnet: Comparison with Carotid and Peripheral Pressures

Abstract

Objective

Evaluate the feasibility of local aortic distensibility measurement using central pressure estimation in the magnet, simultaneous to aortic imaging with cardiovascular magnetic resonance (CMR).

Methods

We studied 49 asymptomatic subjects (26 men, age 44±18 years). Ascending aortic strain was determined by CMR using automated segmentation of SSFP cine acquisitions. Central pressures were estimated as: 1) carotid pressures using tonometry measured immediately after CMR; 2) estimated from brachial cuff pressure using Vicorder™ acquired simultaneously with aortic cine imaging in the magnet. Central pressures were used to calculate aortic distensibility defined as aortic strain over central pulse pressure (AAD-carotid using carotid pressure and AAD-vicorder using Vicorder) and the carotid augmentation index (AIx). Carotid-femoral pulse wave velocity (cfPWV) was measured using tonometry.

Results

Average±SD systolic brachial, carotid and Vicorder pressures were respectively: 114±13, 105±13, 106±14mmHg. We found a strong linear relationship between AAD-carotid and AAD-vicorder (β=0.89, R2=0.91, p<0.001). The mean distensibility difference between the two methods was: −1.1±12 mmHg and variability 0.9%. Distensibilities measured using brachial pressures were higher than using either central pressures (Table).

The correlations with age, AIx and cfPWV obtained using AAD-vicorder (respectively: r=−0.82, r=−0.62; r=0.61; p<0.001) were significantly higher than using AAD-carotid (r=−0.79, r=−0.50, r=−0.58; p<0.001).

Conclusions

Aortic distensibility may be measured by CMR using central pressures measured in the magnet, simultaneously with cine acquisitions. Resulting distensibilities are closely related to those using carotid pressures measured by tonometry outside the magnet and achieve higher correlation with age and markers of global aortic stiffness such as AIx and cfPWV.

Table Average ascending aortic distensibilities according to central pressure measurement technique and age group